Some conventional coffee-making machines commonly used in offices or in restaurants are provided with a water reservoir connected to the mains water supply, a heating element in the reservoir and various heat and flow controls so that an appropriate quantity of hot water is available for coffee brewing purposes. The ground coffee is contained in a removable filter basket disposed below the outlet of the hot water reservoir. When it is desired to brew a pot of coffee, a control is switched so that hot water from the reservoir exits through the ground coffee and the filter basket into a stored pot located on a warming plate below the filter basket. The reservoir is eventually filled with water and reheated, ready for brewing another pot of coffee. These machines often also include an external faucet in communication with the reservoir to allow cups of hot water to be withdrawn from the reservoir.
There are several disadvantages associated with such coffee-making machines. It is common to provide a reservoir of known volume substantially greater than that of the coffee pot so that an appropriate amount of hot water is delivered through the ground coffee to make a full pot of coffee whilst leaving a substantial amount of water in the reservoir. The refilling of the reservoir is normally controlled by a timer mechanism which opens a water inlet valve to the reservoir for a preset period of time prearranged to refill the reservoir. Such an arrangement often leads to insufficient refilling of the reservoir since the timer mechanism cannot take into account variations in the mains water pressure. Moreover the withdrawal of small cups of water from the faucet is not compensated by the timer mechanism. Both of these factors commonly lead to brewing of a short pot of overly strong coffee.
Moreover, conventional coffee-making machines tend to be deficient in their temperature control of the water in the reservoir. It is desirable to contact the ground coffee with water at a temperature between 195.degree. F. and 205.degree. F. These machines typically employ a mechanical thermostat in the reservoir which must be set lower than this temperature to allow a margin of safety against boiling over. Unfortunately, these thermostats react slowly to cooling water and must often tolerate a temperature decline of between 10.degree. F. to 15.degree. F. before reheating. Some heat is lost in the delivery of the water from the reservoir to the ground coffee. As a result, conventional coffee-making machines deliver water to ground coffee at a temperature of about 180.degree. F. to 185.degree. F.
U.S. Pat. No. 5,063,836 to Patel and assigned to Cafe 98 Industries Ltd. discloses a coffee-making machine designed to overcome the above-identified problems. This coffee-making machine includes a reservoir in which is located a heating element. Upper and lower level sensors are in the reservoir and detect the water level in the reservoir. A temperature sensor is also located in the reservoir while a valved inlet acts between the reservoir and the mains water supply. A control circuit communicates with the heating element, the upper and lower level sensors, the temperature sensor and the valved inlet. The circuit operates the heating element when the temperature of the water in the reservoir falls below a predetermined temperature. The control circuit opens the valved inlet when the water level in the reservoir falls below the lower level sensor and closes the valved inlet when the water level reaches the lower level sensor. If the lower level sensor fails, the upper level sensor causes the control circuit to close the valved inlet when the upper level sensor comes into contact with water.
Since level sensors are used in the reservoir instead of a timer mechanism, the water level in the reservoir is always sufficient to ensure enough water to brew a full pot of coffee. Also, the temperature sensor, heating element and control circuit operate to maintain the temperature of the water in the reservoir at a temperature of between 205.degree. F. and 210.degree. F., sufficiently above that achieved with conventional coffee-making machines.
When operated to brew a pot of coffee, the coffee-making machine delivers hot water in the reservoir through ground coffee held in the filter basket located below the spray head. The brewed coffee drips from the filter basket and is either received in a coffee pot located on a warmer plate below the filter basket or a thermal server of the type shown in U.S. Pat. No. 5,038,959 to Patel and assigned to Cafe 98 Industries Ltd, the contents of which is incorporated herein by reference. The thermal server allows the brewed coffee to enter the server without removing the lid of the server. This in conjunction with the lid design minimizes heat loss and therefore, this server maintains the brewed coffee hot for extended periods of time without requiring a heating element.
Although this coffee-making machine and thermal server work satisfactorily, the dimensions of the coffee-making machine sometimes make it awkward to use, especially on kitchen counters with overhead cupboards. Typically, these kitchens designs are prefabricated with the clearance between the counter and the bottom of the overhead cupboards being an industry standard which is smaller than the vertical dimension of the coffee-making machine.
It is therefore an object of the present invention to provide a novel coffee-making machine which obviates or mitigates at least some of the above disadvantages while still ensuring sufficient water in the reservoir to brew a full pot of coffee and maintaining the temperature of the water contacting the ground coffee at a temperature above most conventional coffee-making machines.